In this case, I would attempt to track down all of the splitters and replace any splitters that are under 900MHz.

If you refer to a channel/frequency chart, you can see why a low rated splitter would cause fuzzy pictures.

For example, if you have a 300MHz splitter somewhere, channels 37 and up would not look too great.

A 500MHz splitter wouldn't cause any noticeable problems if your cable channels don't go above channel 70 (which describes most cities). HOWEVER, cable modems usually run from 500 to 900, so you can see that there would be a problem.

Oh, and before someone tries and prove me wrong, I do know that many cable companies will run some sort of programming on channels 95 through 99, and even with a 300Mhz splitter, they'll look perfectly fine. Take a look at the channel chart, and you'll see that those channels actually run from 90MHz to 120Mhz. Nice try. ;)